set_blocksize: Allow to set a larger block size than PAGE_SIZE

set_blocksize is changed to allow to specify a blocksize larger than a
page. If that occurs then we switch the device to use compound pages.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
 fs/block_dev.c |   21 ++++++++++++++-------
 fs/buffer.c    |    2 +-
 fs/inode.c     |    7 +++++++
 3 files changed, 22 insertions(+), 8 deletions(-)

Index: linux-2.6.21-rc7-mm1/fs/block_dev.c
===================================================================
--- linux-2.6.21-rc7-mm1.orig/fs/block_dev.c	2007-04-24 13:19:10.000000000 -0700
+++ linux-2.6.21-rc7-mm1/fs/block_dev.c	2007-04-25 08:08:54.000000000 -0700
@@ -65,12 +65,11 @@ static void kill_bdev(struct block_devic
 		return;
 	invalidate_bh_lrus();
 	truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
-}	
+}
 
 int set_blocksize(struct block_device *bdev, int size)
 {
-	/* Size must be a power of two, and between 512 and PAGE_SIZE */
-	if (size > PAGE_SIZE || size < 512 || !is_power_of_2(size))
+	if (size < 512 || !is_power_of_2(size))
 		return -EINVAL;
 
 	/* Size cannot be smaller than the size supported by the device */
@@ -79,10 +78,16 @@ int set_blocksize(struct block_device *b
 
 	/* Don't change the size if it is same as current */
 	if (bdev->bd_block_size != size) {
+		int bits = blksize_bits(size);
+		struct address_space *mapping =
+			bdev->bd_inode->i_mapping;
+
 		sync_blockdev(bdev);
-		bdev->bd_block_size = size;
-		bdev->bd_inode->i_blkbits = blksize_bits(size);
 		kill_bdev(bdev);
+		bdev->bd_block_size = size;
+		bdev->bd_inode->i_blkbits = bits;
+		set_mapping_order(mapping,
+			bits < PAGE_SHIFT ? 0 : bits - PAGE_SHIFT);
 	}
 	return 0;
 }
@@ -93,8 +98,10 @@ int sb_set_blocksize(struct super_block 
 {
 	if (set_blocksize(sb->s_bdev, size))
 		return 0;
-	/* If we get here, we know size is power of two
-	 * and it's value is between 512 and PAGE_SIZE */
+	/*
+	 * If we get here, we know size is power of two
+	 * and it's value is larger than 512
+	 */
 	sb->s_blocksize = size;
 	sb->s_blocksize_bits = blksize_bits(size);
 	return sb->s_blocksize;
Index: linux-2.6.21-rc7-mm1/fs/buffer.c
===================================================================
--- linux-2.6.21-rc7-mm1.orig/fs/buffer.c	2007-04-25 07:57:35.000000000 -0700
+++ linux-2.6.21-rc7-mm1/fs/buffer.c	2007-04-25 08:06:50.000000000 -0700
@@ -1086,7 +1086,7 @@ __getblk_slow(struct block_device *bdev,
 {
 	/* Size must be multiple of hard sectorsize */
 	if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
-			(size < 512 || size > PAGE_SIZE))) {
+			size < 512)) {
 		printk(KERN_ERR "getblk(): invalid block size %d requested\n",
 					size);
 		printk(KERN_ERR "hardsect size: %d\n",
Index: linux-2.6.21-rc7-mm1/fs/inode.c
===================================================================
--- linux-2.6.21-rc7-mm1.orig/fs/inode.c	2007-04-24 13:19:10.000000000 -0700
+++ linux-2.6.21-rc7-mm1/fs/inode.c	2007-04-25 08:08:01.000000000 -0700
@@ -155,6 +155,13 @@ static struct inode *alloc_inode(struct 
  		mapping->host = inode;
 		mapping->flags = 0;
 		mapping_set_gfp_mask(mapping, GFP_HIGH_MOVABLE);
+
+		if (inode->i_blkbits > PAGE_SHIFT)
+			set_mapping_order(mapping,
+				inode->i_blkbits - PAGE_SHIFT);
+		else
+			set_mapping_order(mapping, 0);
+
 		mapping->assoc_mapping = NULL;
 		mapping->backing_dev_info = &default_backing_dev_info;